Tumour necrosis factor (TNF-α) was first found in the serum of mice and rabbits which had been infected with Bacillus Calmette-Guerin and which had been injected with endotoxin, and was recognized on the basis of its cytotoxic and antitumor properties (Carswell, E. A., et al., Proc. Natl. Acad. Sci. 25:3666–3670 (1975)). It is produced particularly by activated macrophages and monocytes.
Numerous types of cells which are targets of TNF have surface receptors with a high affinity for this polypeptide (Old, L. J., Nature 326:330–331 (1987)); it was assumed that lymphotoxin (TNF-β) binds to the same receptor (Aggarwal, B. B., et al., Nature 318:655–667 (1985); Gullberg, U., et al., Eur. J. Haematol. 39:241–251 (1987)). TNF-α is identical to a factor referred to as cachectin (Beutler, B., et al., Nature 316:552–554 (1985)) which suppresses lipoprotein lipase and results in hypertriglyceridaemia in chronically inflammatory and malignant diseases (Torti, F. M. et al., Nature 229:867–869 (1985); Mahoney, J. R., et al., J. Immunol. 134:1673–1675 (1985)). TNF-α would appear to be involved in growth regulation and in the differentiation and function of cells which are involved in inflammation, immune processes, and hematopoieses.
TNF can have a positive effect on the host organism by stimulating neutrophils (Shalaby, M. R., et al., J. Immunol. 135:2069–2073 (1985); Klebanoff, S. J., et al., J. Immunol. 136:4220–4225 (1986)) and monocytes and by inhibiting the replication of viruses (Mestan, J., et al., Nature 323:816–819 (1986); Wong, G. H. W., et al., Nature 323:819–822 (1986)). Moreover, TNF-α activates the immune defenses against parasites and acts directly and/or indirectly as a mediator in immune reactions, inflammatory processes, and other processes in the body, although the mechanisms by which it works have not yet been clarified in a number of cases. However, the administration of TNF-α (Cerami, A., et al., Immunol. Today 9:28–31 (1988)) can also be accompanied by harmful phenomena (Tracey, K. J., et al., Science 234:470–474 (1986)) such as shock and tissue damage, which can be remedied by means of antibodies against TNF-α (Tracey, K. J., et al., Nature 330:662–666 (1987)).
A number of observations lead one to conclude that endogenously released TNF-α is involved in various pathological conditions. Thus, TNF-α appears to be a mediator of cachexia which can occur in chronically invasive, e.g., parasitic, diseases. TNF-α also appears to play a major part in the pathogenesis of shock caused by gram negative bacteria (endotoxic shock); it would also appear to be implicated in some if not all the effects of lipopolysaccharides (Beutler B., et al., Ann. Rev. Biochem. 57:505–18 (1988)). TNF has also been postulated to have a function in the tissue damage which occurs in inflammatory processes in the joints and other tissues, and in the lethality and morbidity of the graft-versus-host reaction (GVHR, Transplant Rejection (Piguet, P. F., et al., Immunobiol. 175:27 (1987)). A correlation has also been reported between the concentration of TNF in the serum and the fatal outcome of meningococcal diseases (Waage, A., et al., Lancet 1:355–357 (1987)).
It has also been observed that the administration of TNF-α over a lengthy period causes a state of anorexia and malnutrition which has symptoms similar to those of cachexia, which accompany neoplastic and chronic infectious diseases (Oliff A., et al., Cell 555–63 (1987)).
It has been reported that a protein derived from the urine of fever patients has a TNF inhibiting activity; the effect of this protein is presumed to be due to a competitive mechanism at the level of the receptors (similar to the effect of the interleukin-1 inhibitor (Seckinger, P., et al., J. Immunol. 139:1546–1549 (1987); Seckinger P., et al., J. Exp. Med., 1511–16 (1988)).
EP-A2 308 378 describes a TNF inhibiting protein obtained from human urine. Its activity was demonstrated in the urine of healthy and ill subjects and determined on the basis of its ability to inhibit the binding of TNF-α to its receptors on human HeLa cells and FS 11 fibroblasts and the cytotoxic effect of TNF-α on murine A9 cells. The protein was purified until it became substantially homogeneous and characterized by its N-terminus. This patent publication does indeed outline some theoretically possible methods of obtaining the DNA coding for the protein and the recombinant protein itself; however, there is no concrete information as to which of the theoretically possible solutions is successful.